Increasing Clearance

Lower branches often have to be removed to clear them from traffic, to prune them away from a building or walk, make signs visible that were installed too far off the ground, or open up a desirable view. Shortening or thinning limbs in large trees is preferred over removal because of the negative health impacts of large limb removal.

Avoid the following when raising the crown:

  • removed limbs are not too large (preferably less than four inches in diameter)

  • not all branches are removed at one time

  • many branches are not removed from the same spot

The easiest way to raise a crown is to structurally prune a tree over time to keep low branches small.

A word of caution:

Removing too many low branches shifts future growth to the top of the tree. Wind is stronger there, and with no low branches, crown movement at the top of the tree can not be counter-acted, or damped, by the removed lower branches. Too much raising also causes dysfunctional wood leading to cracks and possibly decay inside the trunk. Removing too many lower branches can result in sunburn on the lower trunk and causes sprouting on the trunk and remaining limbs.

The trees to the right have been pruned too high, with less than 60% of the trunk covered with live branches. Trees should not be pruned up beyond the necessary clearance height.

A tall tree with green leaves in front of a parking lot filled with various cars. The sky is very blue. The tree trunk shows many round wounds from previous pruning cuts.
Tall trees with multiple trunks in front of a shopping center. The branches are all leafless except at the very top of the tree.

The live crown ratio should be at least sixty percent, meaning that there should be live branches along the upper sixty percent of the trunk to distribute wind stress and develop trunk taper for stability and strength. Some major branches should be left on the lower one-half of the trunk. Similarly, half the foliage on scaffold limbs should originate from secondary branches on the lower two-thirds of these limbs where practical.

Lions-tailing is not synonymous with crown raising and is considered inappropriate pruning. Removing up to about fifty percent of the foliage and associated branches from the lower crown on conifers has little impact on subsequent growth and movement in wind. In contrast, thinning the top half of the crown would have a greater effect.

Diagram of a tree with labels indicating the different parts: secondary branches, scaffolding branches, and the trunk. The diagram illustrates the proportion of leafy branches is at least 50% of the tree height.

Structural pruning to create a tree with a single straight leader and proportionally small branches will make raising the crown easier and less damaging to the tree. Structural pruning allows trees to develop a form like those shown on the left, being easier to raise.

Pro Tip: Structural pruning helps raising the crown

Street scene with a large leafy tree, parked red cars, and a building with blue and brick exterior. The tree has a single upright trunk.

Most easy to raise

Dominant trunk, small branches

Easy to raise

Dominant trunk only one upright large branch; remove the large lower limb

Tree in front of a blue commercial building with large windows. The tree is bare on the bottom, and has one upward growing trunk and narrow side branches diverging.
A tree in front of a building with a car passing by on the street. The tree has two upward growing branches about 10' off the ground.

Difficult to raise

Several codominant, upright stems

Very difficult to raise

Three wide-spreading limbs; retain branches to avoid large wound areas, resulting in poor defects and structural instability

Tree where trunk diverges into three equally sized upward growing branches about 6 feet off the ground. These branches are bare until about 15' off the ground.
Large leafy tree in a parking lot with buildings and cars in the background. The blue sky is visible in gaps in the foliage.

What branches to cut?

Remove or shorten large low branches rather than secondary branches

Oak recently raised by removing secondary branches

Very wide leafy green tree in a parking lot with parked cars and building in background.

Oak four years later continues to provide clearance issues

To begin a program that will help solve the clearance issue, low limbs should be removed now, and those in the mid-crown shortened with reduction cuts. This encourages growth in the center and top portion of the crown which places the tree on a program aimed at a permanent solution. The goal is to eventually develop branches that will clear the vehicles without the need for large pruning cuts. Although removal cuts made now low on the trunk will be large causing some trunk dysfunction, they will be even larger years from now if the pruning shown above continues. Under the current program, low branches are forced to grow very long so they sag and droop because removal of interior branches is restricting development of taper.

Do not prune several large branches all at once

Close-up of a mature pine tree trunk with several cut branches and rough red-brown bark.

Recently— and overly— pruned tree

Several large wounds puts stress on the tree and exposes it to pathogens. The close-up of the trunk to the right shows six or seven fairly sizable removal cuts at the trunk. It's best for the tree if this large pruning dose is spread across more than one pruning event a year or more apart.

Better yet, a tree would have a regular regimen of structural pruning to prevent the occurrence of several large branches low on the tree.

Large oak tree in a parking lot, with cars and a building in the background under a clear blue sky. The lower part of the trunk is bare of leaves, and has many circular would where branches were pruned.
Tall tree with green leaves and branches against a clear blue sky. Many circular wounds along the trunk show where branches were pruned.

Close-up of oak

Recently-raised oak

Prioritize shorting a large limb to removing secondary branches

Instead of pruning the secondary branches along the lower portion of the two or three largest limbs in the lower crown, the ends could have been reduced in length. This would have helped provide long-term clearance under the tree by exposing branches growing from the leader to more sunligh, thus encouraging growth higher in the tree. Shortening these upright-growing branches also would have slowed their growth which prepares the tree better for their eventual removal. Pruning in the manner shown here also induces the poor form associated with poorly-tapered, long limbs.